1. Field of the Invention
The present invention relates to a deposition mask and a method for manufacturing an organic light emitting display (OLED) using the deposition mask. More particularly, the invention relates to a deposition mask that can be used in depositing an organic emission layer (EML) and a method for manufacturing the OLED with such an EML.
2. Description of the Related Art
An OLED typically includes a first electrode formed in a predetermined pattern on a transparent insulation substrate, an organic film formed by, for example, vacuum deposition on the first electrode, and a second electrode formed on an upper surface of the organic film.
The first electrode is generally made of a transparent conductor such as indium tin oxide (ITO) or indium zinc oxide (IZO) and pattering of the transparent conductor is typically performed by a photolithography method.
Photolithography can be used before the organic film is formed but may not be used after the organic film is formed. This is because the organic film may be very vulnerable to moisture and thus may require thorough isolation from moisture during and after the manufacturing process. Therefore, photolithography that exposes the organic film to moisture during a resist exfoliation or etching may not be appropriate for patterning the organic film and the second electrode.
To solve the above-described problem, the organic film and the second electrode layer may be manufactured by vacuum deposition using a mask having a predetermined pattern. Particularly, the second electrode can be patterned using a cathode separator which is a predetermined isolation wall. However, a small molecular organic film may be most appropriately patterned by vacuum deposition using a deposition mask.
An emission layer (EML) may be manufactured by a method in which respective pixels of red (R), green (G), and blue (B) are independently deposited on a substrate so as to provide a full color display. Since the respective colors are independently deposited, separate masks may be required for each color.
As shown in FIG. 1, four panel regions 11 may be deposited on a substrate 10. The respective panel regions 11 can be formed on one substrate 10 and can be cut off and used separately. Only four panel regions have been formed in FIG. 1, but a further larger number of panel regions can be simultaneously manufactured in a real process. A panel region can refer to a region where an OLED is formed on the substrate.
In FIG. 1, the OLEDs formed on the respective panel regions 11 can have an icon part 12 and a main image part 13. The icon part 12 can have red, green, and blue light emission regions 12R, 12G, and 12B. The main image part 13 can be configured so as to realize full color display.
To deposit EMLs of these elements red, green, and blue masks 14R, 14G, and 14B may be used, as illustrated in FIGS. 2A through 2C. The respective masks 14R, 14G, and 14B may have icon masking parts 15R, 15G, and 15B for depositing the icon part 12 and may have main masking parts 16R, 16G, and 16B for depositing the main image part 13.
If the EMLs are deposited using the respective masks 14R, 14G, and 14B, only portions that correspond to the respective colors of the EMLs may be opened and the other portions may be blocked off in the mask as illustrated in FIGS. 2A through 2C. The portions blocked-off by the mask might be touched by the EML already deposited or other hole transport layer (HTL) or hole injection layer (HIL) during deposition process of the EML. This can damage the organic film. The damage might act as a dark spot afterwards.
As described above, the blocked-off portion of the mask can contact the organic film. In such a case, particles of material forming the organic film might fall onto a region where light emission occurs and have a negative influence on the organic film.
Japanese patent publication No. 2003-257650 discloses a structure in which a spacer (made of insulation body) is formed in a region where light emission does not occur. However, even in that case, a blocked-off portion of the mask may touch the spacer and thus small fragments (and fragments of the spacer) and outgasing may have a negative influence on the organic film.